This application is related to and claims priority from Japanese Patent applications No. 2000-327509 filed on Oct. 26, 2000, and No. 2000-374290 filed on Dec. 8, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a vehicle air conditioner which performs air-conditioning control in a passenger compartment by estimating thermal feeling of a passenger.
2. Description of Related Art
U.S. Pat. No. 5,187,943 discloses a vehicle air conditioner which performs air-conditioning control based on a passenger""s thermal feeling estimated by using a face skin temperature of the passenger, detected by an infrared ray sensor (surface temperature sensor). In the conventional air conditioner, it is important how the face skin temperature of the passenger is accurately detected. Actually, a direction of the face of the passenger is changed, and the face moves in an up-down direction and in a right-left direction. Therefore, the face is sometimes displaced outside a detection area of the infrared sensor. Therefore, the face skin temperature of the passenger cannot be accurately and stably detected, and it is difficult to always accurately estimate the thermal feeling of the passenger.
On the other hand, JP-A-11-157324 discloses a vehicle air conditioner which automatically controls an air outlet mode in the following manner in order to improve heating feeling in a warming-up control operation. Because a temperature of conditioned air blown into a passenger compartment is very low at an initial time in the warming-up control operation, cool feeling is given to the passenger by the conditioned air when the conditioned air is blown to the upper half body of the passenger. Accordingly, in this conventional air conditioner, a foot mode, where conditioned air is not blown toward the upper half body of the passenger, is set at the initial time in the warming-up control operation. Thereafter, as the temperature of conditioned air is increased, the air outlet mode is changed from the foot mode to a bi-level mode, thereby warming hands of the passenger as fast as possible. Then, when the temperature of the conditioned air is further increased, the air outlet mode is again changed from the bi-level mode to the foot mode, thereby preventing warm air from being blown toward the upper side of the passenger compartment from a face air outlet. However, the bi-level mode is switched to again the foot mode based on a detection result of an environmental condition such as solar radiation intensity, inside air temperature and outside air temperature. Therefore, the switching time sometimes does not correspond to the thermal feeling of the passenger and deteriorates air-conditioning feeling of the passenger. For example, the thermal feeling of the passenger is greatly changed between a case where solar radiation directly reaches to the passenger and a case where solar radiation does not directly reach to the passenger even when solar radiation intensity detected by a solar radiation sensor is not changed therebetween. Accordingly, if the air outlet mode switching is performed when the solar radiation intensity detected by the solar radiation sensor becomes equal to a predetermined intensity, cool feeling or hot feeling may be given to the passenger, thereby deteriorating air-conditioning feeling.
In view of the foregoing problems, it is a first object of the present invention to provide a vehicle air conditioner which can always perform an accurate estimation of thermal feeling of a passenger and can perform comfortable air-conditioning control.
It is a second object of the present invention to provide a vehicle air conditioner which can perform a switching from a first mode such as a bi-level mode to a second mode such as a foot mode at a time sufficiently adapting to thermal feeling of a passenger.
According to an aspect of the present invention, in a vehicle air conditioner, a surface temperature sensor is disposed for detecting a surface temperature on a clothes portion of a passenger and for outputting a clothes temperature signal, estimation-value calculating means calculates an estimation value of thermal feeling for a passenger in the passenger compartment based on the clothes temperature signal, and a control unit performs air-conditioning control in the passenger compartment based on the estimation value of the thermal feeling. The clothes portion has a larger area than a face portion of the passenger, and a movement distance of the clothes portion is smaller than that of the face portion of the passenger in a seating condition. Therefore, irrespective of movement, a physique, seating posture and the like of the passenger, the clothes portion hardly deviates from a temperature detection range of the surface temperature sensor, and the surface temperature can be accurately and stably detected. Accordingly, the thermal feeling can be always accurately estimated, thereby always accurately performing air-conditioning control based on the thermal feeling.
Since a change of surface temperature relative to a change of the thermal feeling is larger on the clothes portion than that on the face skin portion, surface temperature of the clothes portion can be more readily used as a control signal.
Preferably, the control unit performs the air-conditioning control in the passenger compartment, in accordance with a difference between the estimation valve, and a target value of the thermal feeling that is an estimation value of target thermal feeling comfortable for the passenger, in such a manner that the estimation value of the thermal feeling coincides with the target value of the thermal feeling. Because the air-conditioning is performed so that the estimation value of the thermal feeling coincides with the target value of the thermal feeling, air-conditioning control comfortable for the passenger can be readily performed.
According to an another aspect of the present invention, a surface temperature sensor is disposed for detecting a surface temperature of a passenger in the passenger compartment, and a mode switching unit is disposed to automatically switch one of a first mode where air is blown at least toward an upper side of the passenger in the passenger compartment, and a second mode where air is blown at least toward a lower side of the passenger while a flow of air blown toward the upper side of the passenger is interrupted. In addition, the mode switching unit switches between the first mode and the second mode based on the surface temperature of the passenger detected by the surface temperature sensor. That is, switching operation between the first mode and the second mode is performed based on the surface temperature of the passenger which is information having strong correlation with the thermal feeling of the passenger. Therefore, one of the first mode and the second mode can be readily switched at a suitable time corresponding to the thermal feeling of the passenger.
Preferably, when the surface temperature of the passenger is lower than a first predetermined temperature in a warming-up control operation where temperature of air blown into the passenger compartment is increased after heating in the passenger compartment is started, the first mode is selected by the mode switching unit. On the other hand, when the surface temperature of the passenger is higher than the first predetermined temperature in the warming-up control operation, the second mode is selected by the mode switching unit. Accordingly, when heating is started, hands and the likes of the passenger can be rapidly heated using the first mode, and a heating acceleration effect can be ensured in the upper half body of the passenger. On the other hand, heating feeling can be also prevented from being uncomfortable due to the first mode.
Alternatively, a vehicle air conditioner includes a first mode switching unit for switching one of a plurality of modes in accordance with an air-conditioning condition, a surface temperature sensor for detecting a surface temperature of the passenger in the passenger compartment, and a second mode switching unit for switching one of a first mode and a second mode in accordance with the surface temperature of the passenger detected by the surface temperature sensor. The plurality of modes at least including the first mode where air is blown at least toward an upper side of a passenger in the passenger compartment, and the second mode where air is blown at least toward a lower side of the passenger while a flow of air blown toward the upper side of the passenger is interrupted. In addition, the first mode switching unit switches one of the plurality of modes in an air-conditioning stationary operation, and the second mode switching unit switches one of the first mode and the second mode in a warming-up control operation where temperature of air is increased after heating in the passenger compartment is started. Accordingly, the air-conditioning control can be suitably performed, while comfortable thermal feeling is given to the passenger.